1. Technical Field
The present disclosure relates to a locking device for an operating mechanism of a gas insulated switchgear, and more particularly, a locking device for an operating mechanism of a gas insulated switchgear, capable of locking or unlocking operations of an operating mechanism of disconnecting switches and earthing switches of the gas insulated switchgear.
2. Description of the Related Art
In general, a gas insulated switchgear (GIS) is an electric device which is installed between a power source side and a load side of a circuit of an electric power system. The gas insulated switchgear switches a circuit on purpose in a normal usage state or safely interrupts current when a fault current such as a ground fault or a short-circuit occurs to thus protect such electric power system and a load device. The gas insulated switchgear is generally used for an ultra-high electric power system.
The gas insulated switchgear generally includes a bushing unit receiving electric energy (power) from a high voltage power source, a circuit breaker (CB), a disconnecting switch (DS), an earthing switch (ES), a moving unit, a controller and the like.
FIGS. 1 and 2 are planar and longitudinal sectional views illustrating a DS and ES unit and an operating mechanism 9 of a gas insulated switchgear according to the related art. The DS and ES unit includes a tank 1 and spacers 2, disconnecting switches 3, earthing switches 4 and three-position switches 5 all disposed in the tank 1, a driving shaft 6 installed at the operating mechanism 9, and a driven shaft 8 operating the 3-position switches 5. A link assembly 7 is provided between the driving shaft 6 and the driven shaft 8.
FIG. 3 is a perspective view of the link assembly 7 of FIG. 1. The link assembly 7 includes a driving shaft lever 7a receiving a driving force of the operating mechanism 9 through the driving shaft 6, a driven shaft lever 7d disposed with being spaced apart from the driving shaft lever 7a and transferring a force to the driven shaft 8, link rods 7b connecting the driving shaft lever 7a to the driven shaft lever 7d to transfer the force from the driving shaft lever 7a to the driven shaft lever 7d, and connection pins 7c rotatably connecting the driving shaft lever 7a or the driven shaft lever 7d to the link rods 7b. 
FIG. 4 illustrates an operation of the link assembly 7. The driving shaft 6 is connected to the driving shaft lever 7a. Movable contacts 5a of the three-position switches 5 are coupled for each phase to the driven shaft 8 coupled to the driven shaft lever 7d. Also, fixed contacts 3a of the disconnecting switches DS and fixed contacts 4a of the earthing switches ES are illustrated. Here, the driven shaft 6, the movable contact 5a, the fixed contact 3a of each disconnecting switch DS and the fixed contact 4a of each earthing switch ES are merely conceptually illustrated for the sake of explanation. When a driving force of the operating mechanism 9 is transferred to the driving shaft lever 7a through the driving shaft 6, the link assembly 7 including the driving shaft lever 7a, the link rods 7b and the driven shaft lever 7d rotates the driven shaft 8. Accordingly, the movable contact 5a of each of the three-position switches 5 coupled to the driven shaft 6 is rotated or slid into one of a closed state of the disconnecting switch DS (DS closed state or position), a neutral (trip) state, and a closed state of the earthing switch ES (ES closed state or position).
FIGS. 5A and 5B, 6A and 6B, and 7A and 7B are views illustrating a case where the driving shaft is in the neutral state, a case where the disconnecting switch is in the closed state, and a case where the earthing switch is in the closed state, respectively, in relation to FIGS. 2 and 3.
Here, the link assembly 7 connecting the driving shaft 6 and the driven shaft 8 to each other has a simple quadric link structure. Also, the link assembly 7 merely serves to transfer the driving force of the operating mechanism 9 to the driven shaft 8 and is not provided with a separate safety device or a locking device. This may be likely to bring about the following problems.
First, while operating (or switching on) the gas insulated switchgear, when a user operates it in an unexpected way carelessly or due to misjudgment, damages on facilities or casualties may be caused.
When the operating mechanism is rotated excessively more or less than a normal rotation angle due to being defectively assembled or other causes, a poor contact (contact trouble) between the movable contact 5a and the fixed contacts 3a and 4a may be brought about, thereby lowering a product performance. In this instance, components may be damaged due to collision between the components.
In addition, when the driving shaft is disassembled or removed to repair or replace the operating mechanism which currently operates, the movable contact 5a may be freely rotated without a restriction due to a non-presence of a supporting structure, and abnormally comes in contact with the fixed contacts 3a and 4a on which current flows, which may be likely to cause an unexpected accident.